The present invention relates to a windshield for a weighing apparatus such as an electronic scale, and particularly to a detachable windshield that can securely be attached to a weighing apparatus and appropriately be attached and detached depending on the intended use by a weighing apparatus user.
In a weighing apparatus, so-called electronic scales including an electromagnetic balancing type weighing apparatus that is called an electronic balance and a high-precision load cell type scale can measure a micro mass, while the electronic scales are largely affected by disturbance. One of the disturbances is airflow around a pan on which a measurement target is placed.
For example, airflow from an air conditioner, human breath during the measurement, and airflow generated by human walk act as a wind pressure on a weight-bearing portion centered on the pan, and the pan is affected by a so-called blast of the wind pressure, which results in an unstable measurement value and a measurement error. Therefore, a windshield that covers the weight-bearing portion centered on the pan is used not only in a high-precision electronic scale called an analytical balance having a minimum scale of about 0.1 mg but also in a model commonly called a general-purpose balance whose minimum scale ranges from about 0.01 g to about 0.001 g.
For the analytical balance, because the windshield is an element necessary to accurately measure a weight, the windshield is formed as part of the electronic scale, that is, the windshield is integral with the electronic scale main body. On the other hand, for the general-purpose balance, frequently the detachable windshield that is formed independently of the electronic scale main body is used in the electronic scale if needed.
In the analytical balance, the windshield integral with the electronic scale main body has an opening and closing portion (hereinafter referred to as “door”) in right and left portions or an upper portion of the windshield, and good usability is achieved. However, the windshield portion becomes inevitably complicated because a frame and a door sliding portion are formed to ensure the opening and closing of the door. Frequently the detachable windshield has a structure simpler than that of the integrated windshield because of demand for light weight and low cost, and frequently the detachable windshield is inferior in usability to the integrated windshield.
In the future, it is believed that the high-precision measurement is increasingly demanded not only in the analytical balance but also in the general-purpose balance, and it is predicted that the distinction between the analytical balance and the general-purpose balance becomes difficult or meaningless as performance of the electronic scale is enhanced in the field of the general-purpose balance. Thus, a need for the windshield is increasingly grown as a whole in the electronic scale.
For example, some proposals of the detachable windshield for the electronic scale, including above-described view point, have been made as follows:
Patent Document 1: Japanese Patent No. 3501857
Patent Document 2: Japanese Patent Application Laid-Open No. 2003-130721
Patent Document 3: Japanese Patent Application Laid-Open No. 10-253435
Patent Document 4: U.S. Pat. No. 4,798,250
Patent Document 5: Japanese Patent No. 3445538